Fair Value of Financial Instruments (Fair Values of Financial Assets and Liabilities on Balance Sheets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jul. 01, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 161,251					$ 115,193	$ 121,449	$ 77,612
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	36,143					31,747
Debt Securities, Held-to-maturity, Fair Value	38,086					32,541
Loans held for sale	7,420					6,499
Cash Surrender Value, Fair Value Disclosure	71,127					69,722
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Valuation Allowance for Impairment of Recognized Servicing Assets, Deductions for Aggregate Write-Downs	0	$ 0	$ 182
Commercial Portfolio Segment
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Financing Receivable, Allowance for Credit Loss	14,085	$ 10,106			$ 4,960
Triumph Premium Finance [Member] | Commercial Portfolio Segment
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Financing Receivable, Allowance for Credit Loss	932			$ 932
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	161,251					115,193
Debt Securities, Held-to-maturity, Fair Value	38,086					32,541
Other investment securities	40,409					42,409
Net loans	3,486,317					3,147,190
Loans held for sale	8,796					6,553
Cash Surrender Value, Fair Value Disclosure	71,127					69,722
Servicing Asset	2,789					3,881
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deposits, Fair Value Disclosure	3,853,468					3,292,950
Short-term Debt, Fair Value	185,713					317,973
Long-term Debt, Fair Value	116,741					82,701
Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	161,251					115,193
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	36,143					31,747
Federal Home Loan Bank ("FHLB") stock	25,022					27,235
Federal Reserve Bank ("FRB") stock	13,311					13,310
Other investment securities	40,409					42,409
Net loans	3,413,957					2,851,969
Servicing Asset	2,489					2,742
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deposits, Fair Value Disclosure	3,952,005					3,291,412
Short-term Debt, Fair Value	182,063					316,977
Long-term Debt, Fair Value	111,386					83,123
States and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	3,545
Debt Securities, Held-to-maturity, Fair Value	4,073					4,791
States and political subdivisions | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	4,073					4,791
States and political subdivisions | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	3,539					4,346
Residential mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	27,879					21,569
Residential mortgage-backed securities | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	27,879					21,569
Residential mortgage-backed securities | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	26,926					21,494
Commercial mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	6,134					6,181
Commercial mortgage-backed securities | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	6,134					6,181
Commercial mortgage-backed securities | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $38,086 at September 30, 2020 and $32,541 at December 31, 2019) (a)(b)	5,678					5,907
Nonqualified Plan [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities	1,711					1,499
Nonqualified Plan [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities	1,711					1,499
Other Security Investments [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities	$ 365					$ 365		$ 0